The orthogonal frequency division multiple access (OFDMA) technology is important for many current communication systems such as Fourth generation (4G) mobile communication systems. These 4G systems target significantly higher sector capacities and higher per user data rates compared to third generation systems. Long Term Evolution (LTE) is one such 4G system and is an evolution of the 3rd Generation Partnership Project (3GPP) Universal Mobile Telecommunications System (UMTS) standard. Other 4G system may include the IEEE 802.16m or WiMAX. All these 4G systems may use air interface technologies based on the OFDMA. LTE uses OFDMA in the downlink (DL) and single carrier frequency division multiple access (SC-FDMA) in the uplink (UL) as the physical layer radio access technology.
In an OFDMA system, the time-frequency two-dimensional electric waves are composed of an Orthogonal Frequency Division Multiplex (OFDM) symbol in the time domain a frequency subchannel in the frequency domain. Each frequency subchannel is composed of a plurality of different subcarriers. In an OFDM symbol time interval, each user in the cell uses an orthogonal frequency subchannel. The OFDMA system is, therefore, free from intra-cell interference, which is an important characteristic of the OFDMA system.
When different cells or users use the same frequency subchannel for transmitting messages in the same time interval, an inter-cell interference (ICI) occurs. Thus, the link quality of the cell edge user degrades and the data throughput decreases, which are serious problems in an OFDMA system. In fact, ICI has been shown to be the predominant performance-limiting factor for wireless cellular networks. As a result, a significant amount of research has been devoted to developing inter-cell interference coordination (ICIC) techniques to reduce and manage the inter-cell interference.